UA1ZBE Custom Firmware v1.0

Features:
- VFO mode with direct frequency input
- POCSAG decoder (512/1200 baud) with BCH(31,21) correction
- Full-screen Spectrum analyzer
- FM Radio receiver
- RSSI signal indicator overlay
- Custom boot splash (UA1ZBE / POCSAG pager / build date)

Architecture:
- app/mode.c — mode dispatcher (VFO/POCSAG/Spectrum/FM)
- app/boot_splash.c — 2-second boot splash
- app/pocsag/ — POCSAG decoder + BCH correction
- app/display_rssi.c — RSSI indicator
- main.c — entry point with custom init
- syscalls.c — bare-metal _sbrk stub

Build: arm-none-eabi-gcc -Os -flto -Wall -Werror -Wextra
Size: 57.9KB Flash / 3.6KB RAM

Controls:
- 0-9: Direct frequency input (VFO)
- SK2: POCSAG mode
- SK1: Spectrum analyzer
- 0: FM Radio
- EXIT: Return to VFO
- F/*: Toggle 512/1200 baud (in POCSAG)

driver/crc.c

@@ -0,0 +1,49 @@
+/* Copyright 2023 Dual Tachyon
+ * https://github.com/DualTachyon
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *     Unless required by applicable law or agreed to in writing, software
+ *     distributed under the License is distributed on an "AS IS" BASIS,
+ *     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *     See the License for the specific language governing permissions and
+ *     limitations under the License.
+ */
+
+#include "../bsp/dp32g030/crc.h"
+#include "crc.h"
+
+void CRC_Init(void)
+{
+	CRC_CR = 0
+		| CRC_CR_CRC_EN_BITS_DISABLE
+		| CRC_CR_INPUT_REV_BITS_NORMAL
+		| CRC_CR_INPUT_INV_BITS_NORMAL
+		| CRC_CR_OUTPUT_REV_BITS_NORMAL
+		| CRC_CR_OUTPUT_INV_BITS_NORMAL
+		| CRC_CR_DATA_WIDTH_BITS_8
+		| CRC_CR_CRC_SEL_BITS_CRC_16_CCITT
+		;
+	CRC_IV = 0;
+}
+
+uint16_t CRC_Calculate(const void *pBuffer, uint16_t Size)
+{
+	const uint8_t *pData = (const uint8_t *)pBuffer;
+	uint16_t i, Crc;
+
+	CRC_CR = (CRC_CR & ~CRC_CR_CRC_EN_MASK) | CRC_CR_CRC_EN_BITS_ENABLE;
+
+	for (i = 0; i < Size; i++) {
+		CRC_DATAIN = pData[i];
+	}
+	Crc = (uint16_t)CRC_DATAOUT;
+
+	CRC_CR = (CRC_CR & ~CRC_CR_CRC_EN_MASK) | CRC_CR_CRC_EN_BITS_DISABLE;
+
+	return Crc;
+}